My guess would be that the notion presented here has occurred to many on the forum, though perhaps not precisely in the form it takes below.
Adjustable Bottom Area Concept
In the diagram is a sketch of a adjustable bottom area surfboard. The board template is actually just an old Clark 7 foot something close-tolerance blank. How it might work should be clear; the tail area adjusts, sort of slips into the forward section, the total adjustment around 5 or 6 inches, the fins moving with the tail section. Basically, you have the option of a shorter board with ‘wings’ or a longer board sans wings. (Sans means without right?)
It’s a sketch, as in - no locking mechanism, no real fin placement, no fine-tuning as to how the structure might be constructed included. So, perhaps you have some thoughts, solutions, problems, etc. with such a concept. If you do I would be interested.
Marketing issues aside, it is nevertheless an interesting technological problem –i.e. seems to call for some ‘natural’ engineering insight, particularly with respect to the locking mechanisms, sections slipping by other sections, etc.
Pros and cons invited – if you’re so inclined.
kc
Additional Note
The notion sort of came to me while trying to decide on what size paddleboard to make - I couldn’t decide. With the paddle board the variation was more like two foot.
kc
Changed Title
The orignal title was ‘Crank Deck Concept’ because I had envisioned a crank to make the adjustment. Then just ‘Adjustable Deck’, which really doesn’t capture the concept, but ‘Adjustable Bottom Area Concept’ seems to work for me.
If I remember right, a planing hull has an immersed area that varies with either weight or speed. If the weight is constant, then more or less speed is gonna change the immersed area.
But here, the adjustment would be made for a given set of conditions (only the two options really, but still…) without having to make an exaggerated change posture (stance) and then accommodate (surf in the new position) for it.
Brave comments from a man who enslaves mollusks - Free the Bivalves! … (they’re bivalves aren’t they?).
But back to your comment.
Sure.
But here you have the option of changing the relationship between available surface area and the other parameters of the board, e.g. winged shortboard, or a bit longer shortboard (sans wings.)
kc
Some Additional Notes
If you surf, watch surfing or just look at a lot of pictures of surfing (and I suspect most have done at least one of those) you might agree that roughly the forward section of modern shortboards and guns, is for paddling and, sort of, splash guard, the tail area is for propulsion. Its almost as though you could make a generic front-end and plug in a bunch of different back-ends. (Which is actually my third post in this thread, but I haven’t posted my second yet.) This of course doesn’t include longboards, at least longboards that are surfed as longboards (i.e. walking the board), which requires a different approach.
After my comments to Doc, I thought it best to get this out of the way.
Basically, using PVC pipes (male into female kind of thing) or whatever, you make up a bunch of tails to pop in for a given set of conditions. Hoaky sure - yet interesting, well at least to me. You could even play with concaves etc. The point being shaping a slew of different tails, or having the option to select a slew of different tails, might be an interesting option.
Kevin, its not exactly what you’re talking about, but I’ve considered for many, many years, the concept of having two Pope-Bisect type boards, with identical profiles right at the center joint.
Imagine a 9’ pintail gun and a 10’ noserider. Both around 22.5" in the middle, by 3.25" thick (I’m a big guy) with soft rails for control.
You would also have a 9’6" speed shape like a Phil Edwards…front half of the gun and back of the NR.
A 9’6" pintail noserider with flat tail rocker for smooth lines like Malibu…Front half of the NR and back half of the gun.
And even maybe a couple interesting double-enders (one even finless)
Or you order 1.5 boards… a roundnose 4.75’ long and two tails - a 5.25’ long squaretail single fin with kick rocker and a 4.25’ long round pin 2+1 with smooth rocker for beachbreaks.
Honestly, I can’t imagine why PB hasn’t done this yet. With machining the boards, its completely doable. I even talked to Thane about it, maybe 6 or 10 years ago (when their boards were still poly handshapes) and he had no interest whatsoever…
(Chuckling) Yeah, well, the nice thing about enslaving bivalves ( yes, they are, primarily M. Mercenaria and C. Virginiatica ) is that they can’t sing protest songs to make me feel guilty about it. Breed 'em, raise 'em, then rip 'em out of the bottom and feed 'em to the Great Unwashed. Or me, if the market ain’t so hot. It’s a beautiful thing.
Now, a thought:
Given ( and horribly oversimplifying ) that a given board has a lift per unit area that varies with the speed, quite likely as the square of the speed, I wonder if a board going at speed V1 has an immersed area of A1, that is (mostly ) independant of trim. Say, something like this:
You’ve seen various sequence pictures of boards in use that show very different immersed parts of the board ( and spray patterns) with pretty much the same trim and speed.
I do agree - you could lop off any part of the board that doesn’t get in the water and it wouldn’t particularly matter, as has been shown by the various lopped off shortboards that work just fine. The tail is the effective planing area.
And on that note, I need to think about supper. Maybe…bivalves…
Like I mentioned Benny, I suspect the idea, possibly in other forms, has occurred to many. I’m not shocked.
That aside, yes, getting a hold of the right Bisect would be a nice front end to play with.
But I’ve seen some of your handy work (albeit in pictures), so my question is, do you think it would be possible to pull off something less than a bisect and reconnect with a twin sliding PVC (male/female) gizmo or some such thing; maybe a foot more towards the tail, than the geometric center?
Separating the ‘paddleboard’ from the ‘surfboard’ is an interesting notion. Think about it, you could chub-up (thickness) the front end for the ‘nutritionally enhanced’ so they could paddle around, but everybody draws from the same pool of tails.
I designed a modular board system a couple of years ago but never built any of it… basicly the concept was to split the board into three segments - tail, mid, nose and have inter connectable pieces so you can mix and match your boards. i.e. you could buy 3 noses, three tails and the mids and have a 27 board quiver. I thought of using a dowl system to connect the peices which whould mean that dufferen dowls could be used for different flex properties (ie, more in tail less in nose. Same all over. etc etc)
the reason I didnt bother is I thought… its just surfing :o)
would still be fun to play with if there was time and money avaiable to prototype…
Its get better, I think its in the Book of Waves by Drew Kampion page 50, there’s a kid surfing a piece of wood (as in plank, as in looks like a piece of siding.)
Your analysis is fine, I would just add the relationship between rocker and template. Also, and I suspect you’d agree, just because things are the way they ‘currently’ are, doesn’t mean design is as efficient as it could be. As I mentioned in my reply to Benny, if it is possible to pull out the ‘paddleboard’ from the ‘surfboard’ then a lot more may be possible.
Then again, I wouldn’t have expected such a ‘liberating’ thought from a slaver – “Their bubbly swishy cries heard from PT to Sandwich… Oh, the horror.“
That’s it alright, but I think you could get away with more by just screwing with the tail-end, structurally that is - less risky, or better able to handle the stress. I know the temptation is to go completely sectional; there’s the transport issue, which is a nice marketing feature, but I’m not really interesting in that aspect of it - which is probably why I’m broke. Like I said in my replies to Benny’s and Doc’s posts, I’m interested in separating the ‘paddleboard’ from the ‘surfboard’ to the highest degree possible - and once separeted, screwing with each accordingly.
How about this for an idea: make a fore and aft insert which adds width to the board. . . that way you keep the rail curve clean and tidy and get to play with width, and bottom area.
With reference to KCaseys initial concept, I’m currently working on a prone-board that has a template so it can be ridden left or right, forward or reverse, so it can be 4 different boards on a single wave.
This is the skin, .6mm birch aircraft 4ply, flip the shape over in your head and you can see it has a fat and a thin tail-end as well as a curvey and a straighter side.
Its a really rounded scalene triangle shape so it looks different from each angle.
SF.
Quote:
You’ve seen various sequence pictures of boards in use that show very different immersed parts of the board ( and spray patterns) with pretty much the same trim and speed.
I do agree - you could lop off any part of the board that doesn’t get in the water and it wouldn’t particularly matter, as has been shown by the various lopped off shortboards that work just fine. The tail is the effective planing area.
doc…
Well I’m part of the fascinated audience, looking forward to the test results
Now about Doc’s comments: although I agree that removing the pointy bit at the nose of a thruster isn’t going to make much difference, for some boards ( not saying which ones exactly ; ) removing the parts that are not in the water is a very bad idea, because it not only removes the swing weight but also part of the driving mass of the board, this negatively affects the ability to penetrate and to have the nose of the board lead down the wave, it also reduces the speed of the board (less mass) . … . there’s also the small point that what may be out of the water at one speed might be in the water at a lesser speed, so, like how much can be removed really ? chop it off when going fast and splat when you slow down ! not a good idea. . . . most boards use all of the board or nearly all of the board at times, so best to leave it there, might need it later.
After my comments to Doc, I thought it best to get this out of the way.
Basically, using PVC pipes (male into female kind of thing) or whatever, you make up a bunch of tails to pop in for a given set of conditions. Hoaky sure - yet interesting, well at least to me. You could even play with concaves etc. The point being shaping a slew of different tails, or having the option to select a slew of different tails, might be an interesting option.
kc
my neighbor has been working on this idea for a few years and has made a few prototypes, he will shit when I tell him about this thread
maybe this is what benny was talking about, but when the pope’s reintroduced their bi-sect i talked to them about doing it in tail area so you could snap on different tails for various conditions…
(one even finless)